Multisignal transmission



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Patented July 27, 1948 MULTISIGNAL TRANSMISSION Lawrence Lee Rauch,Princeton, N. J., assignor to Research Corporation, New York, N. Y., acorporation oi' New York Application December 3, 1945, Serial No.632,578

6 Claims. (Cl. 177-351) The invention relates to a multi-signaltransmission system and particularly to method and apparatus fortransmitting 93511;?, singlwghannel signals from a plurality ofintellgeice sources.

2 character of the signals to be transmitted, Each signal must besampled at a rate high enough to detect variations in the signal. Ingeneral, the sampling rate in samples per second must be An object ofthe invention is the provision of a 5 somewhat greater than two timesthe highest fremethod and apparatus for energizing a plurality quency tobe reproduced. With a signal sampling of intelligence sources to providesignals adapted rate of F times per second and a number of sigto betransmitted on a common transmission nal channels n, the switching speedmust be nF channel. times per second. When high switching speeds Afurther object of the invention is the proare required, mechanicalcommutation becomes vision of a multi-signal transmission systeminadequate. In order to provide eiectively high wherein the frequencyand phase of the signals switching speeds, the transmission systemispreil of the individual intelligence channels are correerably providedwith an electronic commutator b, lated with the rate of sampling of eachintellicomprising a plurality of electronic tube switch j gence channelto provide a high transmission efcircuits corresponding in number to thesignal iiciency. channels to be sampled, the first switch circuit ofWhile the specific features of the invention may the commutator beingactuated by a master pulse be varied to suit the condition of differentprobat the beginning of each switching cycle and the lems, in generalthe invention comprises a methsuccessive switch circuits being actuatedby g od and apparatus for the transmission over a switching pulsescorresponding to the number of single channel of signals from aplurality of insignal channels. telligence sources whereby theintelligence The periodic pulses are passed from each -cf sources areconnected in cyclic serial order with the switch circuits of thecommutator to a moda common output channel at a preselected peulator ofthe invention whereby the correspondriodic sampling frequencyF forsampling periods ing intelligence channel is connected with the having aduration not exceeding l/Fn where n common transmission channel of thesystem duris the number of intelligence signals to be transing theduration of a pulse, thereby, in effect, mitted, and the intelligencesources are energized modulating each pulse with the intelligence sig.with a common alternating potential having a nal. The modulator orconverter may comprise frequency not less than one-half F and, preferatriode, to the plate of which an intelligence sigably, not more than Fnand having a fixed phase nal is applied and to the grid of whichperiodic relation to the sampling periods. positive pulses are appliedwhereby the intelli- The method and apparatus of the invention gencesignal is passed by the triade for the duraare particularly useful insystems for transmittion of the pulse. ting data, such as instrumentreading, strain The invention will be more particularly degauge andaccelerometer readings and the like, scribed with reference to theaccompanying to ground stations for recording and, ior the purdrawingsshowing an illustrative embodiment of pose of illustrating theprinciples of the inventhe invention. tion, the invention will be moreparticularly de- In the drawings: scribed with reference to a system forthe tele- Fig. 1 iS a blOck diagram 0f a multi-signal metering ofaircraft iiight data from a plurality transmitter embodying the methodand appa of instruments to a ground station, more fully ratus of theinvention; l described in application Serial No. 625,590, filed Fig. 2is a block diagram of a receiving system October 30, 1945, adapted toreceive and segregate the signals The transmission system speciiicallydescribed transmitted by the transmitter of Fig- 1; herein includes anelectronic commutator adapt- Fig. 3 is a circuit diagram of the pulsegeneraed to connect in cyclic serial order a plurality of tor of thetransmission system of Fig. 1; intelligence channels with a singleoutput chan- Fig. 4 is a circuit diagram of the bridge circuit nel forradio transmission to a receiver which and amplier of the transmissionsystem of Fig. 1 may include a similar commutator adapted to and lconnect the received signals in corresponding Figs. 5, 6 and 7 arediagrammatic representacyclic serial order to a plurality of indicatingtions of the relations between the source enerand/or recording devices.gizing voltage and the sampling pulses when the The speciiiccharacteristics of the transmission frequency of the energizing voltageis F11/2, Fn system are largely governed by the number and and F/2,respectively. L

The transmission system A typical airborne transmission system is showndiagrammatically in Fig. 1. It operates at a sampling frequency F of1111 per second. Eighteen signal channels, n, are provided fortransmission of signals from eighteen strain gauge bridges A1, A:distributed at critical points on the aircraft. The switching frequencyor pulse frequency, Fn, is therefore 20,000 per second.

The pulse generator B, shown in detail in Fig. 3, provides a kc. sinewave Cs to drive the strain gauge bridges. It also provides masterpulses Pa at 1111 per second which are fed to the first switch circuitC1 of the commutator, as well as to the transmitter D, and switchingpulses Pb at 20,000 per second which are fed to the commutator switchcircuits C1, C2

Corresponding to each strain gauge bridge there is a converter circuitE1, Ez to which the segregated signal pulses P1, P2 are fed from thecorresponding switch circuits of the commutator at the rate of 1111 persecond. The signal from the strain gauge bridges, amplified by theassociated ampliiers F1, Fz as shown in detail in Fig. 4, are fed to thecorresponding converters and emerge as modulated pulses S1, Si having afrequency of 1111 per second and a pulse duration of 1/2o,ouo of asecond.

The modulated pulses Sa are fed to the blanker G which broadens andclips the switching pulses and inserts them in the signal. The modulatedpulses Sb are then supplied to the transmitter D.

The receiving apparatus A suitable form of receiving apparatus is shownin block diagram in Fig. 2. It comprises a receiver H suitable for thereception of the frequency modulated signals transmitted by thetransmitter. The received signal Sb taken from the discrimnator of thereceiver is fed to the amplifier I and to the pulse selector J.

The amplied signal Sc is fed to the converters L1, L2 which are similarin arrangement and function to the converters E1, E2 of Fig. 1. Themaster pulse Pa from the pulse selector is supplied to the rst triggerchannel K1 of the commutator, While the switching pulses Pb are fed incommon to all of the channels of the commutator. The commutator suppliestimed pulses Q1, Q2 serially to the converters in synchronism with theindividual modulated pulses from the amplier I. These individualmodulated pulses S1, S2 are then fed to corresponding integrators M1,M2

In the integrators the individual modulated pulses are grouped to formintegrated signals T1.

T2 having wave forms corresponding to the variations in the data of theinstruments A1, An of Fig. 1.

The puiser An eifective pulsing circuit ofthe multiplier type is shownin Fig. 3. It is driven by a balanced L. C. oscillator circuit 30 tunedto the sampling frequency of 1111 per second. The 1111 cycle signal fromthe oscillator is amplified, clipped and differentiated in circuit 3|and fed into output cathode follower 32 to give the negative masterpulses Pa.

The 1111 cycle signal is tripled in each of the resonant circuits andclass C amplifiers 33, 34 to provide a 10,000 cycle signal. This signalis amplied, clipped, differentiated and rectified in circuit 35 and fedinto output cathode follower 36 The bridge circuit An illustrativebridge circuit and amplier is shown in Fig. 4. In the circuit shown,each arm of the strain gauge bridge 50 may be an active gauge. Thebridge is driven through a carefully shielded transformer 5I. Apotentiometer 52 provides for initial bridge balancing. The bridgesignal is amplified in two-stage tuned amplier 53 with an overall gainof about ten thousand. controlled by a divider between the triode 5l andthe pentode 55.

In the method and apparatus particularly described with reference toFigs. 1-4, the duration of the positive pulses P1, P2 from thecommutators is exactly one-half the period of the 10,000 cycle bridgedriving frequency, and the pulses are phased so that the sampling startswhen the bridge driving voltage is approximately zero and stops when thevoltage is again approximately zero a half period later. Thus, thebridge signal is sampled for half a cycle every eighteenth cycle, asshown in Fig. 5, wherein Cs represents the instrument signal and thesampling .periods S1 are shaded.

Other relations of the sampling pulse to the instrument signal may beused advantageously. For example, by making the sampling pulse durationequal to the period of the instrument signal a complete cycle issampled, as shown at S in Fig. 6. If the number of intelligence channelsn is odd instead of even, alternate or up and down sampling results. Thelatter methods have the advantage of not introducing D. C. componentsinto the signal to be transmitted. An advantageous method .of obtainingthe "up and down" sampling is to energize the intelligence sources withan alternating potential having a frequency of one-half the samplingfrequency F. The phase of the sinusoidal voltages in this methodprogresses from one intelligence source to the next so that each issampled at a peak of the sinusoidal voltage, as shown at S" in Fig. 7.

The amplifying, pulsing, pulse selecting. transmitting, and receivingcircuits shown and described herein are merely illustrative exampleswhich may be widely varied without departing from the principles of theinvention as defined in the claims.

Iclaim:

1. A system for transmitting over a single channel signals from aplurality of intelligence sources comprising means for connecting saidintelligence sources in cyclic serial order with a common output channelat a preselected periodic sampling frequency F for sampling periodshaving a duration not exceeding l/Fn where n is the number ofintelligence signals to be transmitted, and means for energizing saidintelligence sources with a common alternating potential having afrequency not less than one-half F and having a fixed phase relation tosaid sampling periods.

2. A system for transmitting over a. single channel signals from aplurality of intelligence sources comprising means for connecting saidin-4 telligence'sources in cyclic serial order with a common outputchannel at a preselected periodic sampling frequency F for samplingperiods having a duration noil exceeding l/Fn Where n is the 4number ofintelligence signals to be transmitted,

and means for energizing said intelligence sources with a commonalternating potential having a frequency of F11/2 and substantially inphase with said sampling periods.

3. A system for transmitting over a single channel signals from aplurality of intelligence sources comprising means for connecting saidintelligence sources in cyclic serial order with a common output channelat a preselected periodic sampling frequency F for sampling periodshaving a duration not exceeding l/Fn where n is the number ofintelligence signals to be transmitted, and means for energizing saidintelligence sourcesv with a common altern-ating potential having afrequency'of F/Z and having a xed phase relation to said samplingperiods.

4. A system for transmitting over a single channel signals from aplurality of intelligence sources comprising means providing periodicpulses having a frequency Fn where F is the rate at which the signalfrom each intelligence source is to be sampled and n is a whole numbernot less than the number of intelligence sources to be sampled, meansfor energizing said intelligence sources with a common alternatingpotential having a frequency not less than one-half F and having lafixed phase relation to said periodic pulses, and means for modulatingsaid periodic pulses in cyclic serial order with the signals from saidenergized intelligence sources.

5. In a multi-signal transmission system,

.. tion not exceeding l/Fn where n is `the number of intelligencesignals to be transmitted, and means for energizing said intelligencesources with a common alternating potential having a frequency not lessthan one-half F and having a fixed phase relation to said samplingperiods.

6. In a telemetering system, a plurality of instruments adapted tomodulate a potential applied thereto in response to variations in aphysical quality, means for connecting said instruments in cyclic serialorder with a common output channel at a preselected periodic samplingfrequency F for sampling periods not exceeding 1 /Fn where n is thenumber of said instruments, and means for applying to said instruments acommon alternating potential having a frequency not less than one-half Fand having a fixed phase relation to said sampling periods.

LAWRENCE LEE RAUCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,378,395 Dickson June 19, 19452,381,920 Miller Aug. 14, 1945 2,403,890 Johnson July 9, 1946

